Piston regrooving tool



Oct. ,9, 1951 J. J. WITTMAN PISTON REGROOVING TOOL Filed April 17, 1946 JOSEPH J W/TTMAN Patented ()ct. 9, 1951 UNITED STATES ATENT OFFICE 2,570,416 PISTON REGROOVING TOOL Joseph J. Wittman, Detroit, Mich. Application April 17, 1946, Serial No. 662,736

1 Claim. (Cl. 82-4) i The present invention for'chamfering and similar work on pistons and similar members and is particularly adapted for use as a hand tool by automotive mechanics for regrooving pistons.

It is well known that the surface of a piston ring groove nearest the head of the piston and especially of the top groove becomes worn with use and allows oil to leak past the piston ring. Present equipment available for the high precision truing of piston grooves is expensive and requires the'piston head to be disassembled from the piston rod in order to turn the piston head in a lathe or turning machine while the groove is recut. Consequently only large centrally located machine shops are equipped to do this work and considerable expense and delay is involvedshipping pistons to regrooving shops from outlying districts.

Accordingly a principal object of the present invention is to. provide a. relatively simple and inexpensive hand tool that can be used by garage mechanics to regroove pistons without disassembling the piston from the" connecting rod and without the necessity of a lathe to turn the piston;

Further objects of the present invention are to provide a regrooving tool of the character described that can be quickly adjusted to slip over the piston and which has readily adjustable guide means to insure proper formation and spacing of the recut groove.

Other objects of this invention will appear in the following description and appended claim, reference being had to the accompanying drawingsforming a part of this specification wherein like reference characters designate corresponding parts in the several views.

.Fig. 1 is a top view of'a piston regrooving tool embodying the present invention.

, Fig. 2 is a section view taken in the direction of the'arrows essentially along the line 2-2 of Fig. 1 and is shown in relation to a piston.

Fig. 3 is a section view taken in the direction of the arrows along the line 3-3 of Fig. 2.

Fig.4 is a bottom view of a portion of the tool shown in Fig. 2 and is taken in the direction of the arrows along the line 4 i.

':Fig. 5 is a section view takenin the direction of the arrows along the line 55 of Fig. 2.

Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and relates to a tool adapted contacting surfaces 2. of being practiced or carried out in various "ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Referring to the drawing, Fig. 1 shows a piston regrooving tool embodying the present invention wherein a WOIk receiving frame I0 is formed of a slightly elongated annular casting having the downward extending sides II and I2, Fig. 4. The sides H and I2 give the annulus an essentially U -shaped cross-section, thereby providing a maximum rigidity with a minimum weight. The frame I0 is adapted to fit over the workpiece being regrooved, such as an automobile piston 13, Fig. 2, with the sides H making firm guiding contact with the lands of the piston 13 at opposite ends of the small diameter of said frame H].

The rearward portion of the frame II] is adapted to receive the knurled handle M which has the threaded stud-end solidly screwed'into said frame In as shown, Fig. 2

At opposite ends of the long axis of the frame [0 are the rear guide means l5 and forward guide plate l6.

l1 projecting slightly into the enclosure of the frame 10 and is rigidly secured to said frame H] by the plurality of bolts I B. i

The rearward guide I5 is securely held in place by a screw press arrangement which comprises the vertical screw member 22 having the pad 23 at the lower end thereof and being threaded through the upper portion of the yoke 20, which latter is'secured to the frame In by the plurality of screws 2!. The knurled knob 24 at the upper end of the vertical screw member 22 tightens or loosens the contact between the pad 23 and the rear guard I5 and accordingly either locks the rearguard I 5 by friction contact against movement or allows sliding adjustment thereof within the slot [9 of the yoke 20. To facilitate adjustment, the knob 25 is attached to the guide [5 by the screw 26.

The cutting tool 21 is. supported in the guide frame which is shown generally in Fig. 1 by the arrow 28. The body portion of the guide frame 28 has essentially a rectangular U-shaped crosssection formed by the flat base 29 and two vertical and parallel side pieces 36. An extension from each side piece 30 is secured to the framelfl by the screws 3 I.

The cutting tool 21 is moved in andout be tween the two parallel sides 30 and on the flat base 29 by the worm gear 32 which fits intoa socket at the butt of the cutting tool 21 and is The latter has the two arcuate piston extends between the two parallel side pieces 3 and through the threaded axial opening of a worm driving member which latter comprises in one piece the knurled head 34, the neck 35, the shaft 36, and the annular retaining flange 37. The worm driving member is held in place by the slottedcollar 38 which fits over the shaft 36 between the neck 35 and retaining flange 31 and which is secured to each of the side pieces 30 by the screws 39, Fig. 3. Portions of the base 29 and side pieces 30 adjacent to the collar 38 are cut away to provide a journal and a support for the retaining flange 31. Rotation of the knob 34 drives the worm gear 32 in or outalong the threaded axial opening of the worm driving member. Movement of the cutting tool 21 with the worm gear 32 is allowed by the vertical slot 40 provided in the body portion of said cutting tool 21 for the vertical clamp screw 4| which screws into the frame Hi. The screw 4| is tightened by its knurled head 42 and presses the washer 43 against the top surface of the body of the cutting tool 21 to clamp said tool 27 firmly in place.

It is usually the case in automobile pistons having four piston rings that only the top compression ring groove requires regrooving, but that the bottom-most oil ring receives too much wear to be satisfactorily used as a guide ring. Consequently I have adapted my invention to be guided from the second ring from the bottom, thus leaving a blank ring between the cutting tool 21 and the guides 15 and H5 in the case of four-ring pistons. This choice is arbitrary and may be varied to suit particular requirements.

In pistons of similar design but for different automobiles, the spacing between the top ring groove which requires retruing and the third from top ring groove which I prefer to use'as a guide ring varies in the neighborhood of fiftythousandths of an inch. In order to compensate for this variation and to adapt the regrooving tool embodying the present invention to pistons of slightly different measurements, the cutting tool 21 is adjusted vertically by means of a plurality of shims 44 which are selectively inserted ing regrooving. The tool 21 is then adjusted to the desired cutting depth within the groove to be regrooved by turning the knurled knob 34. Finally the tool 21 is clamped in place by tightening the knob 42, and the device is ready for operation which simpl requires rotating the entire tool around the piston [3 by means of the handle [4.

The cutting tool 21 is adapted to be just slightly over size so as to retrue the groove being regrooved. With each revolution of the regrooving tool about the piston l3, the cutting depth of the tool 21 is readjusted by turning the knurled knob 34 of the worm driving member until finally the retrued groove is cut to the desired depth. It is not necessary to disassemble the piston t3 from its connecting rod to perform the operation of regrooving. The piston l3 need only be securely held in a vice or otherwise be prevented from rotating with the regrooving tool.

I' have'found that the two guides l5 and I3 riding on the bottom wall of the guidegroove of the piston l3 insures proper spacing of the cutting tool 27 which is thus guided to true a groove within high precision measurements. The provision to adjust the guides l5 and I5 and the cutting tool 21 relative to each other also, permits the use of a one-piece casting for the frame [0, thereby securing a degree of rigidity and alignment between the guides and cutting toolwhich i not possible in regrooving tools embodying a split ring or hinged ring in' place .of the Work receiving frame casting If].

I claim:

A tool for regrooving pistons comprisinga substantially elliptical inverted .u-shapedframe having a boss formed-.at one end thereof, a knurled rod forming a handle threadedly connected to said boss in alignment with the major axis of said frame, ayoketmounted on said frame inwardly of said boss and havingta guide plate receivingslot also in alignment with said'major 44 essentially fill the flat bottom of the U-shaped trough of the frame guide 28 and are slotted similarly to the cutting tool 2'! to provide for the vertical clamp screw 4 i.

.In operation the forward guide plates [6 and guide frame 28 are first removed to allow the work receiving frame l9 to slip over the head of the piston l3 to be regrooved. Then the guide plate 16 is fitted on the frame ill in the proper guide groove and is securely bolted in place. The rear guide I5 is' also adjusted to fit snugly within the guide groove of the piston l3 and to press the curved sides thereof firmly against the arcuate surfaces I! of the forward guide plate [6. Thus the piston i3 is firmly held between the sides H of the frame l0 and the guides l5 and H5.

The guide frame 28 for the cutting tool 27 is next assembled on the work receiving frame 10 and the spacing between the guides I5 and I6 and the cutting tool 2'! is adjusted by the proper selection of shims 44 such that while the guides 15' and I6 ride on the bottom wall of the guide groove of the piston l3, the cutting tool 2! will be at the proper level to true the groove requiraxis, a relatively narrow rear guideplate supported on said. frame and. slidable through'said guide plate slot along said major axis, a screw press clamping means on saidyoke for locking said rear guide plate in a .flxed position, an arcuate forward guide plate secured to said frame at the other end thereof with its inner edge extending inwardly of said frame symmetrically with respect to :said major axis'and in the same plane with said rear guide plate, means forming a tool way secured to said. frame" at. its other end with said tool way extending in alignment with said major axis, said tool way com.- prising a base and a'pair of spaced guide arms, acutting tool" slidably mounted in said tool way between said guide arms. in a plane above said forward and. rear: guide plates, a screw means for adjustably moving said'cutting tool in said tool way, and a screw press clamping meansion said frame for locking said cutting tool in a fixed position.

JOSEPH J. WITTMAN.

REFERENCES CITED The following references are of record in. the file of this patent:

UNITED STATES PATENTS Number Name Date 460,884- Nugent Oct. 6,-1891 1,820,792 Funchess Aug. 25,1931 1,848,418 Fall Mar. 8,1932 2,399,309 Anderson 'Apr.'30, 1946 

